1. Field of the Invention
The present invention relates to a steam docking unit of an espresso machine.
2. Prior Art
Steam docking units are conventionally a supplemental component of coffee machines, especially espresso machines; and they are connected to a milk steaming pitcher so that it can conduct the steam and are sealed off from the surroundings. The milk steaming pitcher contains all mechanical elements required for producing milk foam and also the milk. The necessary steam is fed to the milk steaming pitcher through the steam docking unit.
The use of such a milk steaming pitcher has an advantage, among others, that during steaming no steam or steamed milk, which might spray, is released into the surroundings, especially when, instead of a closed milk steaming pitcher, an open vessel is used in which a steam tube is not sufficiently submerged into the foaming liquid or if the milk steaming pitcher does not contain enough liquid.
A steam docking unit, which is intended to steam a liquid such as milk in a closed container using steam that is produced in a coffee machine of the espresso style, is disclosed in, for instance, WO 01/26520 that corresponds to U.S. Publication No. 2003-0051603 A1.
This steam docking unit should be easy to use and maintain and should avoid undesired spraying of liquid during steam treatment. To accomplish this, a known steam docking unit is provided with a steam inlet which can be connected, through a valve comprising a cylindrical slide in a cylindrical body, to a steam outlet which is put into contact with a steam inlet opening of a steam pitcher and is automatically sealed off from the surroundings when this is done by a ring-shaped seal. The valve with its cylindrical body can be raised and lowered by a control lever which is mounted so that it can pivot. Inserting the steaming pitcher into its steam receiving position on the espresso machine forces the control lever into its activation position. When the steaming pitcher is removed, the valve with the cylindrical slide swings upward, thereby closing the valve, which then stops the delivery of steam to the steam outlet. The control lever has an arm with which it operates a switching contact to activate the production of steam in the coffee machine in its operating position when it is lying against the milk steaming pitcher, or to turn it off when the control lever is free of the milk steaming pitcher.
Though this steam docking unit is supposed to stop the delivery of steam when the control lever is in its rest position, undesired release and discharge of residual steam in the immediate area of the steam docking unit can occur when the milk steaming pitcher is removed from the steam docking unit, especially if the connecting steam outlet line downstream of the valve is of a relative large volume.